1. Field of the Invention
The present invention relates generally to global positioning system (GPS) smartphone accessories and more particularly to a GPS device external to a smart device adapted for use with the audio interface of the smart device.
2. Description of the Related Art
Although current, conventional smart devices generally have an internal GPS module, such internal GPS modules are deficient for various applications requiring enhanced navigation capabilities. For example, there are conditions where the internal GPS module is denied (spoofed/jammed) or the internal GPS module needs to be augmented, i.e. inside a building.
Providing an external GPS device for use with a conventional smart device is problematic. The effort usually involves costly software modification to every conventional smart device model to provide functionality. The effort also usually requires a set of elaborate custom cable(s) based on the connector and power configuration of the smart device being connected.
Using a cabled GPS device satisfies product requirements for cases where a wireless connectivity method isn't available for security or reliability concerns. A specific example may be military use of a commercial smart device and integration with an external GPS. There are other cabled options which don't use an audio interface for smart device interfacing; each bringing additional cost and modifications to a stock smart device. This defeats the commercial off the shelf qualities of the smart device. Through fewer smart device modifications, the overall reliability and quality of the solution improves, allowing the use of common software frameworks. One example is the use of the Android Software Development Kit and the portability across all Android devices.
It is known that the audio port of a smart phone can be used as a serial port as discussed in, for example, a) ELECHOUSE, SoftModem for Arduino, Audio Jack Modem for iPhone and Android, Webpages from Elechouse catalog downloaded on Dec. 12, 2012 from http://www.elechouse.com/elechouse/index.php?main_page=product_info&cPath=90_92&products_id=2199, pages 1-6; and, b) ENERGY MICRO, EFM 32—Connect the EFM32 with a Smart Phone through the Audio Jack; Application Note AN0054_Rev1.01 dated 2012 Nov. 12 downloaded from http://cdn.energymicro.com/dl/an/pdf/an0054_efm32_phone_audio_jack_interface.pdf on Dec. 12, 2012, pages 1-19.